A bottle of shampoo can cost four euro or it can cost forty, and the gap is wide enough that most people have stood in the aisle wondering whether the dearer one is genuinely better or just better packaged. The question has only grown louder as salon brands that once stayed behind the chair started turning up on Irish shelves and websites, sold for home use at prices that make you pause.

Brands like Kérastase sit at the premium end of that shift, promising salon results from your own bathroom. The promise is appealing, particularly when a good blow-dry at the salon does not last the week. But it is worth understanding what a shampoo or conditioner can actually do to your hair before deciding whether the spend makes sense for you. It helps to know what you are actually washing. Each strand is mostly dead protein, wrapped in an outer layer called the cuticle whose overlapping scales lie flat on healthy hair and lift when hair is damaged. Shine is largely a matter of those scales lying flat.

What does shampoo actually do to your hair?

Most of what shampoos and conditioners do happens right there at the surface, smoothing and coating the cuticle rather than rebuilding the strand from within. Research on the effect of washing on hair found that a single use of shampoo and conditioner left the molecular structure of the hair unchanged, with conditioner acting on the outer layers. In other words, products manage the surface; they do not regrow or fundamentally remake the fibre. But that does not make the expensive option pointless.

What are you really paying more for?

A better conditioner can coat more evenly, hold its smoothing effect longer, protect against heat, and simply feel and smell more pleasant, and for someone who colours their hair or uses straighteners daily, that protection has real value. The difference is often in the formulation and the experience rather than in any dramatic structural change. Whether that is worth the price depends entirely on your hair and how much you ask of it. It also pays to read the promises carefully. Cosmetic claims in Ireland and across the EU are not a free-for-all: under EU rules, any claim made about a product must be supported by verifiable evidence and must not mislead. That is a useful thing to keep in mind when a label talks about transformation or repair. The cushion of regulation is real, but the wording is still written to sell, and "restores" usually means "smooths and protects" rather than anything more miraculous.

Spending wisely matters more than spending big. As our earlier guide to wedding hair pointed out, it is easy to get overwhelmed and spend the equivalent of a honeymoon on products and treatments you do not need at all. The same caution applies to any bathroom shelf. Fine, flat hair wants something light; dry or colour-treated hair wants richer conditioning and heat protection; a scalp that flares up needs gentleness over luxury. Matching the product to the problem matters far more than the price on the bottle.

So who should actually spend more on haircare?

The honest answer to whether the splurge is worth it is that it depends on you. If you style hard, colour often, or simply take pleasure in the ritual, a premium range can earn its place. If your hair is healthy and low-maintenance, a cheaper bottle may serve you just as well. The marketing will always promise the moon. Your own hair, and how you treat it the rest of the week, decides the rest.